Question about legality of processing credit cards online

Good afternoon, I am setting up a website for online event registrations. My customers will enter into an agreement with me, where I will setup a website to accept attendee registrations and payments to attend the event through a website. These payments will be processed using my company's merchant account. I will subtract a fee from the amount collected and transfer funds to my customer who is hosting the event. My question is about the legality of this. I am basically using my company's merchant account to accept payments on behalf of another company, which is usually referred to as "credit card factoring," a form of money laundering. There are tons of companies out there doing business similar to mine. For example when you sign up for a PayPal account, you're able to accept credit cards from anyone, using PayPal's merchant account to process the transactions. I'm not sure how they do this legally. Can someone help? Thanks, Aaron